1. Field of the Invention
The present invention relates generally to keys for driving tamper-proof bolts, and more particularly, to an improved key for driving tamper-proof bolts and a method for making the same.
2. Description of the Prior Art
Tamper-proof threaded bolts or locking devices are well known in the art for protecting various devices from unauthorized access or tampering. For example, in U.S. Pat. No. 3,172,282 entitled "Anti-Tampering Cut-Off Valve Cover" and issued to the inventor of the present invention, a tamper-proof housing is disclosed which is particularly adapted to protect a cut-off valve of the type commonly interposed in water and gas service lines. Threaded locking elements or bolts having a hollow head including a transverse notch or aperture through a sidewall of the head are used to fasten together a pair of mating clamp elements which form a tamper-proof housing enclosing the cut-off valve. Also in U.S. Pat. No. 3,743,239, a lock-off valve is disclosed which includes a locking element having an enlarged head and a threaded shank portion which is arranged in a threaded bore of the valve housing. Similarly, U.S. Pat. No. 3,861,180 discloses an electric meter lock ring of the type commercially available from Morlock, Inc., Phoenix, Arizona. The electric meter lock ring includes a locking element with an enlarged head having a cavity and an aperture in the enlarged head communicating with the cavity. Other locking mechanisms, such as bolt locks employing similar locking elements, are also commercially available, for example those supplied by Morlock, Inc., Phoenix, Arizona.
For each of the locking mechanisms mentioned above, a specially designed key unit is used to rotate the locking element or threaded bolt in order to provide access to the protected device. The key is generally described in U.S. Pat. No. 3,172,282 and includes a plunger rod axially slidable within a tubular sleeve, the tubular sleeve having a transverse aperture at one end thereof. A ball is captively held by the tubular sleeve adjacent the transverse aperture. The plunger rod includes a camming surface at one end thereof for camming the ball into the transverse aperture in the tubular sleeve.
In actual operation, the key is inserted into the hollow head of the threaded bolt, and the key is rotated until the transverse aperture in the tubular sleeve is aligned with the transverse notch or aperture in the sidewall of the hollow head. The plunger rod is pushed against the ball and cams it into the transverse aperture in the tubular sleeve and into the notch or aperture in the hollow head of the threaded bolt. In this manner, a positive rotatable driving connection is established between the key and the threaded bolt. Upon rotation of the key, the threaded bolt may be inserted into or withdrawn from a threaded recess for locking or unlocking, respectively, the protected device.
Although the key described above is well suited for driving threaded bolts of the type mentioned above, construction of the key presently requires many steps which consume much time and labor, thereby resulting in significant expense. The steps presently employed to construct such a key include the following:
1. an outer sleeve or key handle is molded having a cylindrical channel through its longitudinal axis, the diameter of the cylindrical channel being slightly smaller than the diameter of the tubular sleeve;
2. the tubular sleeve is machine-pressed into the cylindrical channel of the outer sleeve or key handle;
3. a hole is drilled transversely into the key handle from its outer surface and extending into the tubular sleeve, the hole extending perpendicular to the longitudinal axes of the tubular sleeve and key handle;
4. threads are tapped in the hole drilled in the key handle and tubular sleeve; these threads later engage the threads of a set screw;
5. a flat is machined onto a portion of the plunger rod; the flat, in conjunction with the set screw, prevents the plunger rod from rotating within the tubular sleeve; the flat and set screw also allow the plunger rod to slide axially within the tubular sleeve while preventing the plunger rod from being withdrawn from the tubular sleeve;
6. a rolled metal sleeve or retaining collar is pressed onto one end of the plunger rod opposite the camming surface;
7. the rolled metal sleeve end of the plunger rod is machine pressed into a hole within a metal plunger handle;
8. the plunger rod is inserted into the tubular sleeve and positioned so that the machined flat is aligned with the hole in the tubular sleeve and the threaded hole in the key handle;
9. a set screw is screwed into the threaded hole in the key handle and advanced through the hole in the tubular sleeve until the set screw abuts the machined flat on the plunger rod;
10. an epoxy seal is applied to the threaded hole in the key handle over the set screw to prevent the set screw from being worked loose, whereby the various parts of the key can be integrally maintained.
In view of the steps set forth above, it should be appreciated that such a key can be constructed according to presently known methods only at considerable cost.
Accordingly, it is an object of the present invention to provide an improved key for driving tamper-proof bolts wherein the key may be constructed with far fewer steps than in the prior art, thereby saving considerable amounts of time, labor and expense.
It is another object of the present invention to provide a method of constructing a key for driving tamper-proof bolts, the method requiring far fewer steps than the method used in the prior art, thereby saving considerable amounts of time, labor and expense.